This application is based on application Nos. 2000-261740, 2000-261741, 2000-261739 and 2000-329625 filed in Japan, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a throw-away tip for use in a cutting process, more specifically, it relates to a throw-away tip providing a sensor line for finding wearing down of an edge.
2. Description of Related Art
Throw-away tips are known which are adapted to be attached to a holder or the like to function as a cutting tool. Such a throw-away tip is a disposable tip which is changed, rather than polished for reuse, when its cutting edge is worn out. The throw-away tip has cutting ridges provided on respective corners of a generally planar rectangular or triangular base. When one of the corner cutting ridges is worn out, another of the corner cutting ridges is used. Then, the throw-away tip is changed when all the corner cutting ridges are worn out.
However, it is not easy to check how far the cutting ridges of the throw-away tip have been worn. In view of an operating environment, it is particularly difficult to detect the abrasion degree of a cutting ridge currently used for cutting without interrupting the cutting process.
Conventional methods for detecting the abrasion degree of the cutting ridge are as follows:
(1) The cutting process is interrupted, and the throw-away tip is removed from the holder to be observed the cutting ridge by means of a tool microscope or the like.
(2) The abrasion degree of the cutting ridge is estimated by detecting a phenomenon incidental to the abrasion of the cutting ridge. For example, a reduction in cutting ability, an increase in vibration, occurrence of a noise, or the like is detected by a sensor disposed adjacent a working portion on a machine tool, and the estimation of the abrasion degree is based on a detection signal from the sensor.
In the method (1), however, the cutting process is interrupted, and the abrasion degree of the cutting ridge cannot quantitatively be determined, so that the abrasion detection cannot accurately be performed.
The method (2) requires a complicated detector, and is less reliable with a poor sensitivity for the detection of the abrasion degree.
One approach to these problems is described in Japanese Unexamined Utility Model Publication No. 3-120323 (1991). This publication discloses a throw-away tip having a sensor line of a conductive film provided along a cutting ridge on a flank thereof. It is also disclosed that the sensor line has a width conforming to an allowable abrasion width. In accordance with the throw-away tip disclosed in the publication, the sensor line is worn as the cutting ridge is worn, so that expiration of the life of the cutting ridge can be detected when the sensor line is cut off.
Further, Japanese Unexamined Patent Publication No. 9-38846 (1997) proposes an ordinary cutting tool (not a throw-away tip) which has a thin film circuit on a flank thereof, wherein expiration of the life of the cutting tool is automatically detected by sensing a change in electrical resistance which occurs due to abrasion of the thin film circuit as the flank is worn.
When a sensor line is provided on the throw-away tip described above, as shown in FIG. 21, an unnecessary pattern portion (solidly shaded areas in FIG. 21) is removed by irradiating a beam of laser. In order to provide a sensor line 12 on a flank 8, however, it is necessary to irradiate a beam of laser also to a cutting edge 9 portion used in the cutting process, and for this reason, the irradiated cutting edge 9 portion melts and turns into solid solution again, which undesirably makes a rough surface.
The cutting process is performed by setting cutting feed per revolution, and for example, given 0.2 mm as the feed per revolution, then, cutting resistance is applied on a rake face 5 side 0.2 mm inside from the ridge between the flank 8 and rake face 5. Because a beam of laser is irradiated to a portion where the load is applied, the surface on that portion is made rough, which reduces the cutting strength and causes a minute crack on the cutting edge 9 portion during the cutting operation. Performing the cutting process under such a condition poses a problem that chipping is induced. Also, the occurrence of a minute crack on the cutting edge 9 portion poses a problem that the finishing surface of a workpiece is made rough.
It is therefore an object of the present invention to provide a throw-away tip capable of solving the above problems, and on which a sensor line can be provided without making a rough surface of a cutting edge portion.
Another object of the present invention is to provide a throw-away tip, which eliminates inconveniences caused when the sensor line is provided that chipping readily occurs on the cutting edge portion.
A throw-away tip of the present invention has a rake face formed on a surface of a base and a flank intersecting with the rake face. The intersection ridge between the rake face and flank defines a cutting edge. A sensor line is made out of a conductive film extending along the cutting edge and having a predetermined width. The sensor line is provided in an electrically insulative relation with respect to the base. According to the present invention, one side edge of the sensor line is provided on the flank substantially in parallel with the intersection ridge, while the other side edge of the sensor line is provided on the rake face side from the intersection ridge.
In other words, according to the present invention, the sensor line is provided mainly on the flank along the cutting edge, and partially on the rake face side astride the cutting edge, whereby a narrow region parallel to the cutting edge is formed on the rake face side.
The above arrangement makes it unnecessary to irradiate a beam of laser onto the cutting edge itself when the sensor line is formed by irradiating a beam of laser. Consequently, inconveniences such that the cutting edge becomes rough, a minute crack occurs on the cutting edge, etc. can be eliminated.
The throw-away tip is provided with a pair of contact regions electrically connectable to an external electric circuit, and one end and the other end of the sensor line are connected to these contact regions via a pair of connection lines, respectively. The pair of connection lines pass through the intersection ridge of the base, and therefore, it is preferable to recess the intersection ridge portion of the base where the connection lines pass through.
By recessing the intersection ridge portion where the connection lines pass through, it is possible to prevent the intersection ridge from colliding with a holder when the throw-away tip is attached to the holder, thereby forestalling disconnection of the connection lines passing through the intersection ridge.
The above and other objects, arrangements and advantages of the present invention will become more apparent with the following description of the preferred embodiments with reference to the accompanying drawings.